常用字符串函数

/*******************************************************************************一.NSString

*******************************************************************************/

/*----------------创建字符串的方法----------------*///1、创建常量字符串。

NSString *astring = @"Welcome to beijing";

//2、通过实例化方法initWithString:实例化一个字符串对象

NSString *astring = [[NSString alloc] initWithString:@" I love iOS!"];NSLog(@"astring:%@",astring);
[astring release];

//3、用标准c创建字符串:initWithCString:encoding:方法

const char *cString = "I love iphone";

NSString* aString = [[NSStringalloc]initWithCString:cStringencoding:NSUTF8StringEncoding];
NSLog(@"astring:%@",aString);
[aString release];

或者:用initWithUTF8String:实例化一个字符串对象const char *p = " Welcome to Beijing!";
NSString *string = [[NSString alloc]initWithUTF8String:p];

//4、创建格式化字符串:占位符(由一个%加一个字符组成)

int age = 23;
NSString *astring = [[NSString alloc] initWithFormat:@”I am %d”,age]];NSLog(@"astring:%@",astring);
[astring release];

//5、通过静态方法创建字符串对象

NSString * str1 = [NSString stringWithString:@"I love programming!"];
NSString * str2 = [NSString stringWithUTF8String:" I love programming!"];NSString * str3 = [NSString stringWithFormat:@"%@",@" I love programming!"];

//6.从文件读取字符串:initWithContentsOfFile:

NSString *path = @" /Users/qianfeng/Desktop/StringAPI.pdf"; //文件路径NSString *astring = [[NSString alloc] initWithContentsOfFile:path];NSLog(@"astring:%@",astring);
[astring release];

/*----------------比较两个字符串----------------*///用C比较:strcmp函数

char string1[] = "string!";
char string2[] = "string!";if(strcmp(string1, string2) = = 0){

NSLog(@"1");}

//1. isEqualToString方法 判断两个字符串是否相等 相等返回1不等返回0

NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 isEqualToString:astring02];NSLog(@"result:%d",result);

//2. compare方法(compare:返回的三种值 分别是-1,0,1)

//NSOrderedSame判断两者内容是否相同
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedSame;//0NSLog(@"result:%d",result);

//NSOrderedAscending判断两对象值的大小(按字母顺序进行比较,astring01小于astring02为真)
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"this is a String!";

BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;NSLog(@"result:%d",result); //
//NSOrderedDescending判断两对象值的大小(按字母顺序进行比较,astring01大于astring02为真)

NSString *astring01 = @"this is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedDescending;NSLog(@"result:%d",result);

//3.不考虑大小写比较字符串
NSString *astring01 = @"this is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 caseInsensitiveCompare:astring02] = =NSOrderedSame;
NSLog(@"result:%d",result);
enum_NSComparisonResult {
NSOrderedAscending = -1, //astring01 小于 astring02NSOrderedSame,astring01 等于 astring02NSOrderedDescendingastring01 大于 astring02};

/*----------------改变字符串的大小写----------------*/NSString *string1 = @"A String";

NSString *string2 = @"String";

//1. uppercaseString小写转大写string1指向的对象内容不会发生改变(会产生一个新的字符串对象,string指向这个新的对象)
NSString *string = [string1 uppercaseString];
NSLog(@"string:%@",string);

//2. lowercaseString大写转小写string = [string1 lowercaseString];NSLog(@"string:%@",string);

//3. capitalizedString单词首字母大写 其余小写,其他字符保持不变NSLog(@"string:%@",string);//首字母大小

/*----------------搜索子串----------------*/

NSString *string1 = @"I love iOS very much!";
NSString *string2 = @"iOS";
NSRange range = [string1 rangeOfString:string2]; //NSRange代表一个范围:子串string2在长串string1中的范围(位置和长度)
NSUIntegerlocation=range.location;
NSUIntegerlength= range.length;
NSString *astring = [NSStringstringWithFormat:@"Location:%lu,Leight:%lu",location, length];NSLog(@"astring:%@",astring);
[astring release];

/*----------------抽取子串----------------*/
//1. -substringToIndex:从字符串的开头一直截取到指定的位置,但不包括该位

置的字符

NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringToIndex:3];NSLog(@"string2:%@",string2);

//2. -substringFromIndex:从指定位置开始(包括指定位置的字符)提取,并包括之后的全部字符 直到最后;

NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringFromIndex:3];NSLog(@"string2:%@",string2);

//3. -substringWithRange: //在指定范围内从字符串中截取子串

NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)];NSLog(@"string2:%@",string2);

/*------------判断字符串内是否还包含别的字符串(前缀,后缀)------------*///01:检查字符串是否以另一个字符串开头- (BOOL) hasPrefix: (NSString *)

aString;(判断前缀)

NSString *String1 = @"NSStringInformation.txt";
[String1 hasPrefix:@"NSString"] = = 1 ? NSLog(@"YES") : NSLog(@"NO");//02:检查字符串是否以另一个字符串结尾- (BOOL) hasSuffix: (NSString *)aString; (判断后缀)
[String1 hasSuffix:@".txt"] = = 1 ? NSLog(@"YES") : NSLog(@"NO");

/******************************************************************************

二.NSMutableString*******************************************************************************/

/*---------------给字符串分配预设空间大小----------------*///stringWithCapacity:

NSMutableString *string;
string = [NSMutableString stringWithCapacity:20];//预设一个20字节的字符串空间
string.string = @”Welcome to qianfeng”;

/*---------------增加字符串----------------*/
//1. appendString: appendFormat:追加,在后面追加字符串

NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is aNSMutableString"];

//[String1 appendString:@", I will be adding some characters"];
[String1 appendFormat:[NSString stringWithFormat:@", I will be adding somecharacters"]];
NSLog(@"String1:%@",String1);

//2. -insertString: atIndex:在指定位置插入字符串

NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is aNSMutableString"];
[String1 insertString:@"Hi! " atIndex:0];
NSLog(@"String1:%@",String1);

/*--------在已有字符串中按照所给出范围和长度删除字符------*/

//deleteCharactersInRange:在指定范围内删除字符串
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a

NSMutableString"];
[String1 deleteCharactersInRange:NSMakeRange(0, 5)];NSLog(@"String1:%@",String1);

/*--------修改字符串------*///-setString:修改字符串

NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is aNSMutableString"];
[String1 setString:@"Hello Word!"];
NSLog(@"String1:%@",String1);

/*--------在指定范围内,替换的原有的字符------*/// replaceCharactersInRange: withString: 替换

NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is aNSMutableString"];
[String1 replaceCharactersInRange:NSMakeRange(0, 4) withString:@"That"];NSLog(@"String1:%@",String1);